Excessive Soot Buildup.........2004 Honda BF30

[walexa]

Hello and good morning to all.....I am a new member and this is my first post.<br /><br />I purchased a 2004 Honda 30hp back in February, and since new it builds up lots of black soot all around the idle exhaust port. I cleaned it up once, but it keeps coming back. I took it in for its first service at about 20 hours and the guy said the plugs looked bad when he changed them. I have seen other Honda outboards, but have never seen one soot up like mine. My thoughts beside the jetting being too rich from the factory are only that the pitch on the prop could be too aggressive........and not allowing the engine to rev into its correct rpm range at WOT. If I pin the throttle in neutral, I can tell where the engine rpm limiter is at, but I have no tach to test my engine while on the water. The engine is on a 1542 jon boat.....350 pounds empty, with 2 grown men, 2 deep cycle marine batteries, and another 200 lbs or so in gear. The prop is the solar stainless 10X12. Any information is greatly appreciated. <br /><br />Waylan

 

[DJ]

Re: Excessive Soot Buildup.........2004 Honda BF30

 

[walexa]

Re: Excessive Soot Buildup.........2004 Honda BF30

DJ,<br /><br />Thanks for your response. Maybe if I give a little more information we could possibly rule out the motor not revving high enough: <br /><br />I have noticed that once on plane, the boat responds very quickly to throttle response. Also, I have noticed that the boat will get to about the same speed whether there are 2 or 3 people in the boat. The motor "sounds" like it is operating in the correct rpm range.....based on where it hits the rev-limiter in neutral, but an engine under load sounds different than one without load. I guess I realize I need a tachometer to verify for sure, I was just hoping that maybe someone else had experienced a similar problem and had a solution or something.

 

[radsrh]

Re: Excessive Soot Buildup.........2004 Honda BF30

First I would never ever pin the throttle in neutral, there is nothing worse than taking a new motor and free spinning it up to and hitting the rev limiter. Next get the tiny tach and see what you are running at wot, if that is in range go to the carbs.

 

[walexa]

Re: Excessive Soot Buildup.........2004 Honda BF30

radsrh,<br /><br />The motor has around 50 hours on it by now..........so it is broken in. I have never heard of any harm done by taking an engine to the rev-limit in neutral......isn't that what a rev-limiter is there for? Anyway, I will get a tiny tach and go from there.

 

[DJ]

Re: Excessive Soot Buildup.........2004 Honda BF30

 

[walexa]

Re: Excessive Soot Buildup.........2004 Honda BF30

Most rev limiters have a pretty good safety factor on them........afterall, that's what they're there for. And yes, I have done that to every vehicle I have ever owned........no damage. Anyway, I will get a tiny tach and go from there. Thanks to all, and I will report back my findings.

 

[walexa]

Re: Excessive Soot Buildup.........2004 Honda BF30

Ok........got a tiny tach and my motor is making about 5800 to 5900 rpm at WOT. Since my engine makes 30 HP at 6000 rpm, is it safe to say that the soot buildup is not due to overloading the motor? What carburetor adjustments could be made to reduce the soot buildup? I am not sure at what throttle setting that the buildup occurs since my rpm constantly changes. Any help is greatly appreciated.

 

[LubeDude]

Re: Excessive Soot Buildup.........2004 Honda BF30

Originally posted by walexa:<br />Most rev limiters have a pretty good safety factor on them........afterall, that's what they're there for. And yes, I have done that to every vehicle I have ever owned........no damage. .

You have the wrong conception of what a rev limiter is "there for", and quit reving your engines with out a load on them to the limiter or you are someday going to pay for it. The limiter is ther so you do not over rev UNDER LOAD.

 

[walexa]

Re: Excessive Soot Buildup.........2004 Honda BF30

LubeDude and anyone else worried about me overrevving my engine:<br /><br />I am sorry that I have apparently stepped on some toes by taking my Honda outboard to the rev limiter in neutral......this has not been my intent. However, are any of you engineers for Honda? Is there a page in the owners manual or even a service manual that specifically states to not take the engine to the rev limiter under no-load circumstances? Unless someone can give me more factual evidence that this is wrong, how can you expect me to believe any different. It is not like I crank my engine on a freezing cold morning and pin the throttle for 5 minutes......I have only taken it there for a couple seconds at a time to see where the limit is. <br /><br />Back to the post........anybody have any experience with a Honda producing too much soot?

 

[MajBach]

Re: Excessive Soot Buildup.........2004 Honda BF30

I am certainly no expert compared to most on this board but a few thought run through my mind. My Honda 90 has the two exhaust ports, one in the prop and the other higher - thats the same with yours right? I too get soot around mine but not enough that any more than a swipe with a damp rag won't get rid of.<br />How do you define 'bad' for the condition of the plugs? They were sooty?<br />Are you using the motor at higher than usual altitudes? Do you do a lot of trolling by comparison to most? That's when the exhaust comes out of the upper port. <br />How heavy is the oil you use? Maybe switch to a hotter plug?<br />Just thoughts.

 

[LubeDude]

Re: Excessive Soot Buildup.........2004 Honda BF30

Originally posted by walexa:<br /> However, are any of you engineers for Honda? Is there a page in the owners manual or even a service manual that specifically states to not take the engine to the rev limiter under no-load circumstances?

So why dont you just get on the phone and call your Honda dealer and ask him what he thinks? When he quits laughing, he will tell you not to do it any more! Then when you are done with that one you can call the dealer of the car you drive and ask to talk to a mechanic, then when he stops laughing, he also will tell you not to do it!<br /><br />We may not all be engineers here on the forum, but we do know a thing or two!

 

[walexa]

Re: Excessive Soot Buildup.........2004 Honda BF30

MajBach,<br /><br />Thanks for your response. The soot is coming from the upper exhaust port, which I believe is called the idle exhaust port. Mine built up pretty bad the first night out, and I washed it off. Since then, I have not cleaned it off.......just so that when I take it back to the dealership, they will see exactly what I am talking about. It does idle for a couple minutes at a time when we are putting out hooks and such, but then we are full throttle to put out another hook. There is some mid range running as well. I am using the 5w-30 oil which is what the manual recommends. When I asked my dealer about brand or weight, they had no preference. As far as the plugs go, I am only going by what the service guy told me when he changed them.......he said they were carboned up. I would like to get a service manual and see what it has to say. <br /><br />To Lubejob: FYI: I don't know everything and I don't claim to either, but I am a mechanical engineer, and have taken design courses, and have a cousin (who is also a mechanical engineer) who worked for an engine manufacturer.........rev limiters are there to prevent engine damage under any over-rev conditions, regardless of whether the engine is loaded or not. So, unless you can offer some concrete evidence that is contrary to this, go to another forum or post and argue why the motor oil you prefer is superior.

 

[LubeDude]

Re: Excessive Soot Buildup.........2004 Honda BF30

Hmmmmmmm, Didnt make the call did ya?<br /><br />The main problem with this practice is that it puts a great strain on the valve train, mostly if it has a chain involved. Tensioners will start to flutter and not be able to compensate for the free reving and can jump timing. Timing belts can start to flap and cause the tensioner to allow the belt to come off causing the same thing. I still contend that its not the best practice. But who am I to tell you what to do, Ive only been around engines of all types my whole life, and actually seen engines screwed up buy some kid showing his buddies how high the engine revs before the rev limiter kicks in, Hard to explain that to dad.<br /><br />But, Hey, Rev on!!!

 

[walexa]

Re: Excessive Soot Buildup.........2004 Honda BF30

Look GoobLube:<br /><br />If you have seen an engine screw up because of that, then first off, you have to consider the age and condition of the engine. If we are talking about an engine with high mileage/hours that is probably ready for the junk yard, then that is one thing. Are you sure the engine you have seen screw up even had a rev limiter? An engine in good mechanical condition with a well-designed rev limiter will never self-destruct, provided it is warmed up and has the correct amount of oil in it........and anybody should expect a late model engine from Honda to be able to handle 6250 rpm without spitting up it's guts. Matter of fact, that engine would probably have to see over 10,000 rpm before coming apart, but I'm not an engineer for Honda either..so that is just my assumption. So, just to satisfy my curiosity and show you are correct, tell us the makes and models and condition of the engines you have seen screwed up by kids taking them to the rev limit.

 

[LubeDude]

Re: Excessive Soot Buildup.........2004 Honda BF30

Agree to disagree! Its off topic anyway

 

[DJ]

Re: Excessive Soot Buildup.........2004 Honda BF30

 

[outboardguy]

Re: Excessive Soot Buildup.........2004 Honda BF30

A little off topic but the current mercury outboards now have a seperate rev limiter for 3000rpm when the engine is in neutral,and a normal rev limiter for in gear operation.My assumption is that they did this to prevent exactly what you are doing.<br /><br />I agree with others that your carboning up problem is most likely carburetor related.Float level,carb synchronization,idle mixture.The idle mixture is set at the factory and for at least my california engines is plugged off for epa reasons.Well you have to think that the factory is as close to sea level as you can get(japan).well when the engines get to my 5500 ft level I sometimes have to remove the plugs and adjust the idle mixture. Good Luck

 

[walexa]

Re: Excessive Soot Buildup.........2004 Honda BF30

DJ and outboardguy, thanks for the responses. I guess I will just take my boat back to the dealership again and let them take another stab at it. Their first response was to run it more and see if it got better. <br /><br />DJ.....normally, anything that could cause engine damage is spelled out in italicized or red or bold letters in most owners manuals. In my Honda owners manual, it states that running the engine with a low oil level can cause engine damage. When I read this, I think......duh.....common sense. It even states that using the starter for more than 5 seconds at a time can overheat and damage the starter motor. To me, the owners manuals tend to error on the side of caution, kind of like McDonalds now putting the "very hot" warning on their coffee cups. Anyway, it is fine that we disagree.<br /><br />outboardguy...the reason the mercury has the 3000 rpm rev limiter in neutral is to try and prevent someone from engaging into forward or reverse with the engine pinned.

 

[BillP]

Re: Excessive Soot Buildup.........2004 Honda BF30

walexa,<br />My hat is off to you for wanting hard data to back up the reving issue. I agree with you that redlining in neutral isn't going to harm MOST motors. However, here's info you and others may recall from mech engineering school...The reason for not high reving in neutral is that ROLLER bearings can skate without a load. They tend to do this when you back down the throttle quickly. Ball bearing don't have that issue. In the past, Honda liked to use ball bearings and high oil pressure but the newer motors I don't know. <br /><br />More interesting info...Several years ago Honda published R&D testing methods about their 4 stroke motorcycle engines. They ran them deep into redline in NEUTRAL for 24 hrs and no problems. Running them 24 hrs on a dyno with full load at redline produced problems. Running higher than speced viscosity oil ran them hotter (often too hot on air cooled engines). <br /><br />Bill